Net calculation simulation failed while building net calculation units

What causes this issue?

Net calculation simulation failed while mapping the selection criteria
to net calculation units.

System Response

The result of the net calculation simulation cannot be determined.

How to fix this error?

Additional messages should allow you to find out the reason of the
failure. If required, contact your system administrator for support.
Net calculation simulation is organized in the following steps:
Mapping of the selection criteria to net calculation units
Net calculation units are the data format used for net calculation
execution and queries.
Gross entitlement and gross payment determination
If required, the entered or changed SSP or SDP data is handled by gross
entitlement and gross payment determination. As a result, a gross
payment document (GPD) is created but not stored in the database. The
GPD is handed over to the next processing step.
Net calculation execution (simulation only)
If a new GPD is available, the net calculation is processed for it.
Query of result
A query is executed to provide the net calculation result for the
entered selection criteria. The data is fetched from the database but
the net calculation result of the prior step is included, if it exists.
If no entered or changed SSP or SDP data is provided, the result of the
net calculation simulation displays the database content. This is the
net calculation result that reflects the current status regarding the
billing process.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.